This invention relates generally to the field of intraocular lenses (IOL) and, more particularly, micro-incision IOLs.
The human eye in its simplest terms functions to provide vision by transmitting light through a clear outer portion called the cornea, and focusing the image by way of a crystalline lens onto a retina. The quality of the focused image depends on many factors including the size and shape of the eye, and the transparency of the cornea and the lens.
When age or disease causes the lens to become less transparent, vision deteriorates because of the diminished light which can be transmitted to the retina. This deficiency in the lens of the eye is medically known as a cataract. An accepted treatment for this condition is surgical removal of the lens and replacement of the lens function by an artificial intraocular lens (IOL).
In the United States, the majority of cataractous lenses are removed by a surgical technique called phacoemulsification. During this procedure, an opening is made in the anterior capsule and a thin phacoemulsification cutting tip is inserted into the diseased lens and vibrated ultrasonically. The vibrating cutting tip liquifies or emulsifies the lens so that the lens may be aspirated out of the eye. The diseased lens, once removed, is replaced by an artificial lens.
For many years, IOLs were made from a hard plastic, such as polymethylmethacrylate. As the optic of the IOL had a diameter of 5.5 mm to 6.5 mm, implanting the IOL required that the incision into the eye be enlarged to a size sufficient to allow the IOL to pass into the anterior chamber of the eye. Such a large incision can induce a distortion in the cornea, or induced astigmatism, post-operatively. More recently, IOL's have increasing been made from soft, foldable materials, such as silicone and soft acrylics. These foldable materials allow the IOL to be implanted through incisions that are generally less than 3 mm. Even the relatively small incision required for implantation of foldable IOLs can induce post-operative astigmatism, so there has been a desire to develop IOLs that can be implanted through even smaller incisions, on the order of 2 mm or less.
From a practical standpoint, there are limits on how small an IOL can be made. For example, the IOL generally must have an optic having a diameter of about 5.5 mm or greater for optimum optical performance. In addition, the IOL must be provided in a large range of optical powers, up to 30 diopters or more. These large powers limit how thin the optic can be made. Of course, increasing the refractive index of the material used to make the optic allows for a thinner optic. Current materials and designs permit the manufacture of very thin optics, having an extremely thin, almost knife-like, edge thickness. These extremely thin lenses, however, tend to be unstable to and distort when implanted within the capsular bag, requiring an encircling ring or equatorial band to be inserted into the capsular bag to help stabilize the capsular bag. The ring component of the IOL can be formed integrally with the optic or implanted as a separate component. If the ring is a separate component, the surgical procedure is increased in complexity because two is separate devices, the ring and the optic must be inserted into the eye, assembled and properly located within the capsular bag. Prior to the present invention, if the ring component is integrally formed with the optic, undesirable size and bulk is added, increased the require size of the incision.
Therefore, a need continues to exist for a safe and stable intraocular lens system that can be inserted through a very small incision and does not require assembly within the eye.